Corresponding author: Shih-Yi Hsiung
Abstruct
I obtained the ultrastructure and the macrostructure of pollen grains
of 23 modern oak species (Quercus sp.) in California using
scanning electron microscope (SEM) and light microscope (LM). These
pollen samples were collected from living trees in the UC Botanical
Garden at Berkeley and the Tilden Regional Park at Berkeley.Quercus pollen is treated as an important high temperature
indicator in the paleopalynological samples. However, the genus is
difficultly identified into species level under light microscopy. Here, I provide the results of ultrastructure and macrostructure
investigation of Quercus pollen grains for the future palynology
studies. Three types of surface texture were recognized in the modern
samples with 60 SEM images. The light microscope (LM) investigations of
710 modern Quercus pollen specimens are reported for comparison.
The measurements include one size measurement, polar axis and equatorial
axis, and two shape measurements, P/E ratio and p/D ratio. I applied T-test on 20 species (excluding hybrid Quercus ,Chrysolepis , and Notholithocarpus ). The results suggest
that there are significant difference between sizes and shapes of each
species, each section, and evergreen-decidous oaks. Then I applied
Moran’s tests on 20 species to test phylogenetic signals. There is only
the length of polar view passed Moran’s test (p <0.05;p = 0.041 and 0.042 in 2 tests) when I tested 20 species at the
same time. It suggested that the length of polar view of the oak pollen
grains contain phylogenetic signals. I also found phylogenetic signal
in the distance between 2 furrows in Lobatae sections, Q. agrifolia, Q.
kelloggii, Q. parvula, and Q. wislizeni (p <0.05;p =0.035). Further investigations will be focused on details of
surface ultrastructure and trait-environment relationships.